1. Field of the Invention
The present invention relates to a method of producing a liquid crystal display device.
2. Description of the Related Art
A liquid crystal display device comprises a first substrate, a second substrate, and a liquid crystal inserted between these substrates. Here, either the first substrate or the second substrate is a TFT substrate comprising TFTs, and the other one is a color filter substrate comprising color filters. An annular seal comprising a photo-curable sealing agent is formed on the first substrate. After the first substrate and the second substrate are bonded together, the annular seal is irradiated with ultraviolet rays to be cured. The liquid crystal is inserted in a region surrounded by the annular seal.
According to a conventional method of producing a liquid crystal display device, an injection hole is formed in the annular seal, and the liquid crystal is injected through the injection hole formed in the annular seal in a vacuum chamber after the first substrate and the second substrate are bonded together. Thereafter, the injection hole in the annular seal is closed, and the annular seal is pressed so as to form a suitable cell gap.
In recent years, there has been proposed a method of producing a liquid crystal display device called a drip injection method (see, for example, Japanese Unexamined Patent Publications (Kokai) No. 8-190099, No. 2000-66163 and No. 11-326857). In the drip injection method, an annular seal is formed on one substrate, and a liquid crystal is dripped in a region inside the annular seal of one substrate. Then, the pair of substrates are bonded together under pressure in a vacuum chamber. Thereafter, the pressure of the substrates is released, the vacuum chamber is opened to the atmosphere, and the annular seal is cured by the irradiation with ultraviolet rays or by a combination of irradiation with ultraviolet rays and heating. The drip injection method makes it possible to reduce the number of steps of production and to lower the cost of producing the liquid crystal display devices.
There has further been proposed the provision of a buffer member in order to improve the non-uniformity of a cell gap caused by the introduction of foreign matter at the time when the pair of substrates are bonded together (see, for example, Japanese Unexamined Patent Publications (Kokai) No. 6-3632).
There has further been proposed an art of attracting and holding the substrates (see, for example, Japanese Unexamined Patent Publications (Kokai) No. 8-169971). In this case, a porous resin sheet is adhered onto a base plate having a ventilation hole, and the substrate is secured to the base plate by vacuum attraction via the porous resin sheet.
In the production of the liquid crystal display device by the drip injection method, electrostatic chucks are used for holding the substrates at the time of bonding the pair of substrates together. However, if foreign matter is introduced to the electrostatic chucks, the foreign matter bites into the substrate causing the cell gap to become defective. After the pair of substrates are bonded together, further, the vacuum chamber is opened to the atmosphere, and the bonded pair of substrates is taken from the electrostatic chucks. At this moment, it often happens that the pair of substrates bonded together is not reliably peeled off from the electrostatic chucks and it is forcibly peeled off, with the result that bonding deviation may occur. This phenomenon happens more conspicuously as the size of the substrates increases.